Process for the manufacture of c-nitrosoarylamines



Patented July 17, 1951 PROS/LESS FOR THE MANUFACTURE 0FC-NITROSOARYLAIWINES Stiles M. Roberts, Easton, Pa., assignor to General Aniline & Film Corporation, New York,

corporation of Delaware No Drawing. Application September 22, 1949,Serial No. 134,595

7 Claims. 1

This invention relates to the manufacture of C-nitrosoarylamines bynitrosation of the corresponding secondary arylamines and rearrangementof the N-nitroso compound. More particularly, it relates to a process ofeffecting the manufacture of the C-nitrosoarylamines by a one-stepprocess directly from the corresponding secondary arylamine. Thisapplication is a continuation-in-part of my co-pending applicationSerial No. 666,532, filed May 1, 1946, now Patent No. 2,495,774.

The rearrangement of N-nitrosoarylamines to their corresponding carbonnitroso derivatives is a well-known process. It has been described asearly as 1886 by O. Fischer in connection with the preparation ofp-nitroso-N-methylaniline, p-nitroso N ethylaniline,p-nitroso-N-ethyl-otoluidine, and 'i-nitrosodiphenylamine in Berichte,volume 19, page 2994. With particular reference to the diarylamines, ithas been found difficult to effect the rearrangement of the N-nitrosoderivative to the C-nitroso compound. It has generally been necessary tofirst convert 1e diarylamine to its N-nitrosoarnine derivative withnitrous acid, isolate this derivative, and then isomerize it bytreatment with anhydrous ethyl alcoholic hydrochloric acid. TheN-nitroso derivative is generally dried after isolation before elfectingthe rearrangement.

The preparation of the C-nitrosodiarylamines, and particularlyl-nitrosodiphenylamine, from thecorresponding secondary diarylamines inone operation without isolation of any intermediate N nitroso compoundis described in U. S. Patent 2,G46,356 by Max Wyler et al. The Wylerprocess carries out the conversion under strictly anhydrous conditions.As a solvent for the diarylamine, there is employed an anhydrousalcohol, for example methyl alcohol, to which the dry hydrogen chlorideis added in an absolute alcohol solution. The required alkali metalnitrite for the conversion is added in dry powdered form. When N-alkylarylamines are used for this conversion, the same reaction can beaccomplished, and was accomplished by O. Fischer, by merely adding acold. concentrated solution of a metal nitrite to an alcoholic hydrogenchloride suspension or solution of the base, but when using thediarylamines with the same reactants, Wyler applied strictly anhydrousconditions in order to accomplish the conversion in a single step.

I have now found that the inherently difficultly convertiblediarylamines can be converted to the carbon nitroso derivatives in asingle step in a much simpler manner and without the necessity of usingdifiicultly obtainable reactants, such as dry hydrogen chloride,absolute alcohol, and dry sodium nitrite, if sulfur dichloride (SClz) orsulfur tetrachloride (SE14) is substituted for the hydrogen chloride. Inthis process I may use commercial grades of alcohol such as the lowmolecular weight aliphatic alcohols which normally contain Water inpercentages of from 1-5. If desired, further amounts of water may beadded and, of course, it is not necessary to use dry reaction vessels.There is no loss in yield and, as a matter of fact, improved yields ofcarbon nitrosodiarylamihes of good quality are ob tained. The process iscarried out in its preferred manner by introducing the sulfur dichlorideinto a suspension of the diarylamine and an alkali metal nitrite in acommercial grade of an alcohol, such as methanol, subsequently drowningthe reaction mixture in an ice water mixture and finally isolating thecarbon nitrosoarylamine by known methods most suitable to the specificamine employed. In some cases, the product may be filtered off as thehydrochloride following the drowning operation.

This process is not restricted to any particular secondary arylamines,but is of particular interest in the case of the diarylamines which aredifficultly convertible in a one-step operation to theC-nitrosodiarylamines. The process may be applied to any secondary'arylamine capable of undergoing the formation of N-nitroso derivativesand rearrangement to C-nitrosoarylamines. Typical examples of compoundswhich are capable of such rearrangement are: diphenylamine, phenyl a.naphthylamine, di-l-naphthylamine, 3-acetylaminodiphenylamine, andi-acetylaminodiphenylamine.

Although it is preferable to add the sulfur dichloride or sulfurtetrachloride to a suspension of the arylamine and alkali metal nitritein an alcohol solution, it is possible to first react the sulfurdichloride or sulfur tetrachloride with the alcohol containing smallportions of water and add the arylamine to this mixture, after which thealkali metal nitrite may be incorporated. The amount of sulfurdichloride or sulfur tetrachloride required to efiect the conversion mayvary, but for best results from 1 to 8 mols should be employed per molof the base. The temperature at which the agent necessary for thenitrosation and rearrangement is added is preferably from 0 to 30 C.

The following example, in which the parts given are by weight unlessotherwise stated, will 3 serve to further illustrate the invention, butis not intended to limit its scope.

Example 1 169 g. of diphenylamine, equal to one gram mol, is dissolvedin 3 360 g. of methanol (commercial) by'warming to 35-45 C. The solutionis cooled to -5 C. and

80 g. of finely divided sodium nitrite is added:

Then over a period of fromj2 -3-hours 240 g. of sulfur dichloride isadded at 0 5 f The mixture is then stirred from 4-6 hours at 0-5 C.,poured into 3000 cc. ice water, stirred one hour, filteredand washedwith water or salt solution. The '4- nitrosodiphenylamine hydrochloride5 thus bbe tained can be transformed into the free base by dissolving itin alkali, filtering from any residue and precipitating the base withacetic acid. This product crystallized from a mixture of benzeneand-petrol ether has a melting point of 145-146 C.' I .1

Example 2 V 169 g. of diphenylamine, equal to one gram mol,

is dissolved in 360 g. of methanol (commercial) by warming to 35-40 C.The solution is cooled at 0-5 C. and

80 g. of finely divided sodium nitrite is added.

Then over a period of from 2-3 hours 400 g.' of sulfur tetrachloride isadded at 0-5 C. The mixture is then stirred from 4-6 hours at 0-5 C;poured into 3000 cc. ice water, stirred one hour, filtered and washedwith water or salt solution. The 4- nitrosodiphenylamine hydrochloridethus obtained can be transformed into the free base by'dissolving it inalkali, filtering from any residue and precipitating the base withacetic acid. This product crystallized from a mixture of benzene andpetrol ether has amelting point of 145-146 C.

maintain the reaction mixture in a substantially 50 anhydrous condition.

2. The process of producing a C-nitroso diarylamine which comprisesintroducing into an aliphatic alcohol media containing an alkali metalnitrite and an unsubstituted diarylamine, sulfur dichloride at atemperature not exceeding 30 C. while utilizing said sulfur dichlorideto react with 5 the water present in the reaction mixture to pro- 'ducehydrogen chloride and maintain the reaction mixture substantiallyanhydrous, drowning the reaction mixture in an ice water mixture andisolating the C-nitroso diarylamine.

l [I 3. Theprocess of producing a C-nitroso diarylamine which comprisesreacting at a temperature not exceeding 30 C. an unsubstituteddiarylamine I and an alkali metal nitrite in methanol in the presence ofsulfur dichloride while utilizing the sulfur dichloride to react withthe water present ato produce hydrogen chloride and maintain thereaction mixture substantially anhydrous, drowning the reaction mixturein an ice water mixture and isolating the resulting C-nitrosodiarylamine.

4. The process as defined in claim 1 wherein the "aliphatic alcoholmedia is commercial methanol.

"5. The process of producing a C-nitifoso-diarylamine which comprisesintroducing sulfur dichloride at a temperature notexceedingBQQ-C.

into suspension of an unsubstituteddiarylamine and an alkali metalnitrite in commercial'm'ethanol while utilizing thesulfur dichloridetofreact with the water present to produce hydrogen chloride andmaintain the reaction mixture sub- Tm stantially anhydrous, drowning thereaction mixture in an ice water mixture and isolating the resultingC-nitroso diarylamine. v

6. The process as defined in claim 1 wherein the unsubstituteddiarylamine is diphenylamine.

'7. In the process of producing a C-nitroso diarylamine by reacting at atemperature not'exceeding C. an unsubstituted diarylamine with an alkalimetal nitrite in an aliphatic alcohol in the presence of hydrogenchloride, the improve-- 40 ment which comprises generating the hydrogenchloride in the reaction mixture by the addition thereto of sulfurdichloride which operates to maintain the reaction mixture in asubstantially anhydrous condition.

STILES M. ROBERTS.

REFERENCES CITED The following references are of record in the file ofthis :patent:

Parkes et al., Mellors Modern Inorganic Chemistry, Longmans, Green 8;Co.; New York, N. Y., new edition 1939, p. 481.

Number

1. THE PROCESS OF PRODUCING A C-NITROSO DIARYLAMINE WHICH COMPRISESREACTING AN ALKALI METAL NITRITE IN AN ALIPHATIC ALCOHOL MEDIUM WITH ANUNSUBSTITUTED DIARYLAMINE IN THE PRESENCE OF A SULFUR CHLORIDE SELECTEDFROM THE GROUP CONSISTING OF SULFUR DICHLORIDE AND SULFUR TETRACHLORIDEAT A TEMPERATURE NOT EXCEEDING 30* C. WHILE UTILIZING SAID SULFURCHLORIDE TO REACT WITH THE WATER PRESENT TO GENERATE HYDROGEN CHLORIDEAND MAINTAIN THE REACTION MIXTURE IN A SUBSTANTIALLY ANHYDROUSCONDITION.